package main

import (
	"fmt"
	"image"
	"image/color"
	"image/gif"
	"io"
	"log"
	"math"
	"math/rand"
	"net/http"
	"strconv"
)

var palette = []color.Color{
	color.White,
	color.Black,
	color.RGBA{0xFF, 0x00, 0x00, 0xFF},
	color.RGBA{0x00, 0xff, 0x00, 0xff},
	color.RGBA{0x00, 0x00, 0xff, 0xff},
}

func main() {
	http.HandleFunc("/", handler)
	http.HandleFunc("/lissajous", func(w http.ResponseWriter, r *http.Request) {
		if err := r.ParseForm(); err != nil {
			http.Error(w, "Error parsing form", http.StatusBadRequest)
			return
		}
		cycles := 5
		if cyclesStr := r.Form.Get("cycles"); cyclesStr != "" {
			c, err := strconv.Atoi(cyclesStr)
			if err != nil {
				http.Error(w, "Invalid cycles parameter", http.StatusBadRequest)
				return
			}
			cycles = c
		}
		fmt.Println("cycles", cycles)
		lissajous(w, cycles)
	})
	log.Fatal(http.ListenAndServe("localhost:4675", nil))
}

func handler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "%s	%s	%s\n", r.Method, r.URL, r.Proto)
	for k, v := range r.Header {
		fmt.Fprintf(w, "Header[%q] = %q\n", k, v)
	}

	fmt.Fprintf(w, "Host = %q\n", r.Host)
	fmt.Fprintf(w, "RemoteAddr = %q\n", r.RemoteAddr)

	if err := r.ParseForm(); err != nil {
		log.Print(err)
	}

	for k, v := range r.Form {
		fmt.Fprintf(w, "Form[%q] = %q\n", k, v)
	}
}

func lissajous(out io.Writer, cycles int) {
	const (
		res     = 0.001
		size    = 100
		nframes = 64
		delay   = 8
	)

	freq := rand.Float64() * 3.0
	anim := gif.GIF{LoopCount: nframes}
	phase := 0.001
	for i := range nframes {
		rect := image.Rect(0, 0, 2*size+1, 2*size+1)
		img := image.NewPaletted(rect, palette)
		index := i % 4
		for t := 0.0; t < float64(cycles)*2*math.Pi; t += res {
			x := math.Sin(t)
			y := math.Sin(t*freq + phase)
			img.SetColorIndex(size+int(x*size+0.5), size+int(y*size+0.5), uint8(index))
		}
		phase += 0.1
		anim.Delay = append(anim.Delay, delay)
		anim.Image = append(anim.Image, img)
	}
	gif.EncodeAll(out, &anim)
}
